WPF:WINDOWS Added ability to update application installed in Program Files folder (#813)

* Updated Windows Example

* Organized usings

* Fix for update application in write protected folder

* Typo fixed

* Examples updated to RNW 0.43.0

* Fixed Warning  CS0108

windows/CodePush/CodePushUtils.cs

@@ -9,6 +9,11 @@ namespace CodePush.ReactNative
 {
     internal partial class CodePushUtils
     {
+        internal static string GetFileBundlePrefix()
+        {
+            return CodePushConstants.FileBundlePrefix;
+        }
+
         internal async static Task<JObject> GetJObjectFromFileAsync(StorageFile file)
         {
             string jsonString = await FileIO.ReadTextAsync(file).AsTask().ConfigureAwait(false);